Melt spinning apparatus



April 28, 1970 TosHlRo ONO T 3,508,296

MELT SPINNING APPARATUS Fled`Jan. 2, 1968 INVENTOR. T OS H l RO ONO ATTORNEY United States Patent O Int. Cl. D01d 5/08 U.S. Cl. 18--8 13 Claims ABSTRACT OF THE DISCLOSURE An apparatus for the melt-spinning of synthetic fibers in lwhich a buffer wall separates the filament bundle from part or all of the inner wall of the quench stack beginning at a point below the cooling air inlet ports. The buffer wall may be constructed of any porous or gauzelike material which is permeable to air currents. By virtue of the spacing between the buffer wall and the inner wall of the quench stack and also the porosity of the buffer wall, fiuid turbulences arising in the region of the filament bundle are mollified.

This application is a continuation-in-part of U.S. Ser. No. 655,360, filed July $24, 1967, now abandoned.

Background of the invention This invention relates to the melt spinning of polymers and cooling of the resultant filaments by means of a current of inert gas. In particular it relates to an improved apparatus for the melt-spinning of polymers by means of which the magnitude of fluid turbulences in the region of the filament bundle is lessened, resulting thereby in filaments of improved quality.

It has been a common practice in the melt spinning of polymers to cool the filaments emerging from the spinneret in a current of inert gas (e.g., air) at a controlled temperature. This solidifies the polymer at a controllable rate and imparts sufficient strength to the filaments to permit winding on a bobbin and other subsequent operations. Usually, such a cooling process is conducted while the filaments '(collectively termed a bundle) are passing through a conduit or quench stack which may be several meters long.

Unfortunately, the filaments constituting the filament bundle tend to shake and sway during their passage through the quench stack so that they occasionally strike one another and may even come into contact with the wall of the quench stack. Since the filaments at this stage are still in a semi-molten or plastic state, such contact with the wall of the quench stack and with other filaments will cause structural variations in the cross-section of the filaments at the points of contact. Such changes in the cross sectional shape (spotting) will impair the drawability and other physical properties of the filaments.

I have found that the erratic behavior of the filament bundle within the quench stack is caused by fluid turbulences. Such turbulences also cause irregular cooling of the filaments Which adds further to the physical deformation thereof.

Summary of the invention Therefore, it is an object of my invention to provide a process for the spinning of molten synthetic polymer and the cooling of the resultant filaments with a current of inert gas.

Another object of my invention is to provide a melt spinning apparatus for the production of yarn filaments of improved quality.

According to my invention, the aforementioned drawbacks are eliminated by means of one or more perforated partitions or buffer walls located Iwithin the quench stack and extending in a direction generally parallel to the axis of the quench stack. The buffer wall is preferably cylindrical and concentric with the quench stack, but it may have any shape so long as it divides the quench stack into at least two compartments. Communication between the compartments is permissible but not preferable. The buffer wall or walls can extend along the entire length of the quench stack or a portion thereof, but must be positioned within the quench stack so as not to interfere with the movement of the filament bundle. Temperature and gas current velocity are not critical in the design or operation of the apparatus of the invention.

The buffer wall of my invention may be made of any material which is perforated, or more generally speaking, permeable to a gas. Such a material must be capable of being shaped into a wall having enough strength to withstand the forces encountered during operation of the melt spinning apparatus. Thus, the thickness of the buffer wall is determined in part by the spacing of the pores in the walls and the diameter of said pores. It has been experienced that the ratio of the pore diameter to the distance between pore centers is between about 0.1 and about 1.0 when the ratio of the thickness of the buffer wall to the pore diameter is between about 0.2 and about 3. The preferred thickness of the buffer wall is between about 0.5 and about 3 mm. Therefore, according to the above preferred relationships the pore diameter can vary between about 0.17 mm. and about l5 mm., but the preferred port diameter is between about 0.6 mm. and about 5 mm. Precautions must be taken however to insure that the buer wall is designed and positioned within the quench stack so that the ratio of the space Within the walls thereof which accommodates the filament bundle to the total area of the pores is not greater than 10. Material suitable for forming the buffer wall of' my invention include fine Iwire mesh screen, metal gauze, and perforated sheet metal.

The buffer wall when designed to conform with the foregoing limitations operates to reduce the amount of turbulence within the quench stack by virtue of having perforations or pores. When a turbulence arises within the locale of a given pore on the buffer wall, a pressure difference arises between that pore and a neighboring pore. In order to reestablish equilibrium, a counter-turbulence is induced within the space between the buffer wall and the wall of the quench stack. This counter-turbulence has a dampening effect upon the original turbulence. The overall effect is the elimination of localized turbulences and prevention of erratic movement of the filaments within the filament bundle.

Other objects and a more complete understanding of my invention may be had by reference to the following description of the drawings and preferred embodiment of the invention.

Brief description of the drawings FIG. 1 is a vertical elevation in section of a preferred embodiment of my invention.

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1.

FIGS. 3 and 4 are modified forms of my invention shown in cross section analogous to FIG. 2.

Description of the preferred embodiments Referring to FIG. 1, filaments 1 emerge from the orifices of spinneret 2 into cylindrical quench stack 4 in a direction gradually convergent upon the axis of quench stack 4. Cooling air enters quench stack 4 through orifices 6 located in cylindrical wall 7 of wind box 8. The cooling air enters quench stack 4 transverse to the direction of motion of filaments 1. Cylindrical wall of quench stack 4 is situated below wall 7 and is separated from filaments 1 by cylindrical buffer wall 12. Buffer wall 12, which is made of a porous or gauze-like material such as punched sheet metal, wire-netting, and the like, is concentric with wall 10 and extends from the lower end of wall 7 of wind box 8 to the vicinity of take-up bobbin 18. The space between filaments 1 and wall 10 is partitioned by buffer wall 12 into cylindrical space 14 and annular space 16. Buffer wall 12 may be held in place by any of a number of means 13 familiar to those skilled in the fastening art, provided however, that such fastening means 13 do not interfere with the operation of buffer wall 12.

During melt-spinning, the filaments 1 emerging from spinneret 2 proceed in a bundle through quench stack 4. Air at a predetermined temperature emerges from cylindrical wall 7 through orifices 6 and cools the filaments during their passage through quench stack 4. A turbulence arising in the vicinity of pore 22 will be dampened by counter-turbulences generated by adjacent pores and 24.

Referring to FIGS. 3 and 4, variations in the design and positioning of buffer wall 12 are shown in cross section.

In FIG. 3, buffer Walls 26 are planar partitions which divide the volume within the quench stack into spaces 28 and 30. Attachment of buffer walls 26 to wall 10 of the quench stack serves as a means of fastening buffer walls 26 in position.

In FIG. 4, single buffer wall 32 is a` planar partition which divides the volume within the quench stack into spaces 34 and 36. Attachment of buffer wall 32 to wall 10 of the quench stack serves as a means of fastening buffer wall 32 in position.

The following examples will more clearly illustrate the advantages of my invention.

EXAMPLE I In the operation of the apparatus in FIG. 1 embodying the features of my invention, a nylon 6I fiber of 225 deniers was obtained by extruding the molten polyamide through spinneret 2 having 15 orifices, at a wind-up rate of 1000 m/min. and at a temperature of 260 C. The filaments emerging from the spinneret were cooled by a transverse stream of air at a temperature of 28 C. and fiowing at the rate of 20 cm./sec. The filaments traveled vertically downward through quench stack 4 within cylindrical buffer wall 12. The buffer wall was made of punched metal having a pore diameter of 2.0 mm. The average distance between adjacent pore centers was 3.5 mm. The filaments were then wound on a bobbin in a conventional manner.

In a test for filament uniformity and evenness, the filaments emerging from the quench stack 4 were tested with a Uster evenness tester. The test was conducted on 120 samples in accordance with ASTM-D1425-60T. The average chart range of Uster evenness for the 120 samples was 1.4% or an average Uster evenness where U=0.7%.

EXAMPLE II Nylon filaments were spun in accordance with the procedure of Example I except a conventional quench stack without a perforated buffer wall was employed. These filaments were tested for uniformness (U) by the pro cedure set forth above. On 120 samples the average chart range of Uster evenness was found to be 2% or =1% which indicates considerably poorer uniformity than for filaments spun in accordance with the present invention.

EXAMPLE III Example I was repeated except in this experiment thp buffer wall was 3 meters in length and positioned within a 4 meter long quench stack intermediate the ends thereof. The buffer walls were 1.0 thick and had pores or apertures therein 1.0 mm. in diameter having an average distance between centers of 2.0 mm.

A measurement of evenness on samples again revealed U :0.7% when spun in a spinning system employing a perforated buffer wall of the type described herein.

It will be noted from the data obtained in the foregoing examples that the filaments spun in accordance with. my invention have 30% less cross-section imperfections of spots as determined by the Uster evenness tester than filaments spun without employment of the buffer wall.

I wish to emphasize that the drawing of the apparatus and the above examples are provided by Way of illustration only, and are not meant to be inclusive. Minor changes in and modifications of the apparatus and operating procedure may be made without departing from the scope of the specification and appended claims.

What is claimed is:

1. A melt spinning apparatus for producing filaments of improved quality comprising a spinneret, a quench stack adapted to permit the passage therethrough of filaments emerging from said spinneret, means situated between the spinneret and the quench stack for exposing the filaments to a current of cooling gas within the quench stack, means for collecting the filaments after passage thereof through the quench stack, and at least one perforated partition positioned within the quench stack and extending in a direction generally parallel to the axis of said quench stack, said partition being so disposed within the quench stack to avoid contact with the filaments passing through the quench stack and having a thickness at least about as small as the average diameter of the perforations.

2. A melt spinning apparatus according to claim 1 wherein the means situated between the spinneret and the quench stack for exposing the laments to a current of cooling gas within the quench stack comprises an annular Wind box surrounding the filaments and having an inner wall adapted to permit the passage of cooling gas, and the perforated partition comprises a cylinder concentric with the axis of the quench stack.

3. A melt-spinning apparatus according to claim 2 wherein the perforated partition comprises a plane intersecting the quench stack.

4. A melt spinning apparatus according to claim 2 wherein the perforated partition is made of a material selected from the group consisting of wire mesh screen, metal gaue, wire netting, and sheet metal.

5. An improved melt-spinning apparatus comprising a spinneret, a quench stack adapted to permit the passage therethrough of filaments emerging from said spinneret, means for exposing the filaments to a current of inert gas within the quench stack, and means for collecting the filaments after passage thereof through the quench stack, the improvement which comprises at least one perforated partition positioned within the quench stack and extending in a direction generally parallel to the axis of said quench stack, said partition being so disposed within the quench stack to avoid contact with the filaments passing through the quench stack and having a thickness at least about as small as the average diameter of the perforations.

6. The improvement according to claim 5 wherein the perforated partition is a cylinder concentric with the axis of the quench stack.

7. The improvement according to claim 5 comprising at least one planar perforated partition intersecting the quench stack which divides said stack into two compartments.

8. The improved apparatus according to claim 5 wherein the ratio of the total area of the stack enclosed by the perforated partition to the total area occupied by the perforations is not greater than 10:1.

9. The improved apparatus according to claim 5 wherein the perforated partition is made of a material selected from the group consisting of wire mesh screen, metal gauze, wire netting, and sheet metal.

10. The improved apparatus according to claim 5 wherewherein the pore diameter is between about 0.6 mm. and in the perforated partition has a multiplicity of pores hav- 5 mming diameters ranging from about 0.17 to 15 mm. References Cited 11. The improved apparatus according to claim 10 UNITED STATES PATENTS wherein the ratio of the thickness of the perforated par- 5 2 252 684 8/1941 Babcock tition to the pore diameter is between about 0.2 and 3. 3067458 12/1962 Daucher.

12. The improved apparatus according to claim 11 3,234,596 2/1966 Sims wherein the perforated partition has a thickness between 3,299,469 6/1967 Charlton about 0.5 mm. and 3 mm.

13. The improved apparatus according to claim 12 10 WILLAM J. STEPHENSON, Primary Examiner 

